I'm not sure what you mean, because Cathedral Windows doesn't need any special ruler. It is a folded pattern. Here is a link to a tutorial.
http://hyena-in-petticoats.blogspot....-tutorial.html
Also, the 10 minute block is a Faux-Cathedral Window, that doesn't need a special ruler.
Circle Magic looks similar, but is not exactly the same. You could use a regular dinner plate for that one.
Good Luck.